Conventional high-power multilevel power converter systems typically utilize multiple bulky laminated copper plates and bus bars as the mechanical structure to support a number of semiconductor switching devices and passive power devices. Such conventional power converter structure exhibits a few drawbacks: (1) low volumetric and gravitational power density, due to the necessity of using a number of bulky laminated copper bus plates and bus bars that are used for interconnecting various bridges and phase legs, as well as the screw-terminal dc capacitors. (2) Large commutation loops with significant parasitic inductance that is caused again by the utilization of numerous bus bars for interconnecting different bridges and phase legs, as well as the mechanical bolts and nuts. Such high-parasitic-inductance large commutation loops are detrimental to the limited voltage withstanding capability of the power devices of the multilevel converters, especially for the power converters configured by fast-switching modern semiconductor devices. (3) The conventional laminated copper bus structure generally integrates the copper plates for all the different voltage levels together, which possesses poor thermal dissipation characteristic for each bus plate.